Indented Tube for a Heat Exchanger

ABSTRACT

A shell tube and heat exchanger ( 10 ) includes a plurality of tubes surrounded by a shell ( 16 ). Each tube ( 12 ) includes a plurality of indentations. A mold is placed in a desired positions and orientation in a die. A tube is placed in a first position within a die, and the mold crimps the tube to form the desired indentation in the tube. The mold is then released, and the tube is moved relative to the mold to a second position. The mold again crimps the tube to form an additional indentation. Alternately, the mold includes a roller that forms a groove on the tube. The tube is translated or both translated and rotated relative to the mold to form the groove.

BACKGROUND OF THE INVENTION

The present invention relates to a method for forming a tube used in aheat exchanger including a plurality of indentations that increase heattransfer between a fluid flowing through the tube and a fluid flowingaround the tube.

A shell and tube heat exchanger is used to cool fluids in variousautomotive applications, including exhaust gas recirculation coolers andpower steering devices. In an engine gas recirculation system, anexhaust fluid flows inside the tube and exchanges heat with a coolantflowing around the tube. The exhaust fluid closer to the tube wall coolsfaster than the exhaust fluid flowing in the center of the tube.

In the prior art, the tubes in the heat exchanger can be bent or twistedto create turbulence in the exhaust fluid and to provide a non-linearflow path to increase heat transfer.

There are several drawbacks to the bent or twisted tubes of the priorart. For one, it is difficult to manufacture the tubes. Additionally, itis both costly and laborious to twist and bend the tubes to the desiredshape.

Hence, there is a need in the art for a method for shaping a tube usedin a heat exchanger that overcomes the drawbacks and shortcomings of theprior art.

SUMMARY OF THE INVENTION

A shell and tube heat exchanger includes a plurality of tubes surroundedby a shell. Each of the tubes includes a plurality of indentations. Acooling fluid flowing through the shell exchanges heat with a hot fluidflowing through the tubes. Preferably, the shell and tube heat exchangeris used in an exhaust gas recirculation system, and an exhaust fluidflows through the tubes and exchanges heat with a coolant flowingthrough the shell.

The tube includes indentations that increase the surface area of thetubes and the amount of fluid located proximate to the walls of thetubes. The indentations also create turbulence in the fluid flowingthrough the tubes.

In one example, a mold of a desired shape is placed in a desiredposition and orientation in a die. The tube is placed in a firstposition within the die, and the mold crimps the tube to form thedesired indentation in the tube. The mold is then released, and the tubeis moved relative to the mold. The mold then again crimps the tube toform an additional indentation. The tube can be translated relative tothe mold or can be both translated and rotated relative to the mold.

Alternately, the mold includes a roller that forms parallel grooves onthe tube. The tube is translated relative to the mold to form thegrooves on the surface of the tube. The number of rollers determines thenumber of grooves. Alternately, the tube is both translated and rotatedrelative to the mold to form a spiral groove on the surface of the tube.

These and other features of the present invention will be bestunderstood from the following specification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a cross-section of a shell and tube heat exchanger;

FIG. 2 illustrates a die for molding a tube of the present invention ina first position;

FIG. 3 illustrates the die for molding the tube in a second position;

FIG. 4 illustrates a perspective view of a first embodiment of the tubeincluding angled indentations;

FIG. 5 illustrates a perspective view of the first embodiment of thetube including parallel indentations;

FIG. 6 illustrates a perspective view of the embodiment of the tubeincluding different angled indentations;

FIG. 7 illustrates a cross-sectional view of a second embodiment of thetube including six grooves;

FIG. 8 illustrates a cross-sectional view of the second embodiment ofthe tube including five grooves;

FIG. 9 illustrates a cross-sectional view of the second embodiment ofthe tube including four grooves; and

FIG. 10 illustrates a perspective view of a third embodiment of theindented tube including a spiral shaped groove.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates a shell and tube heat exchanger 10 including aplurality of tubes 12 surrounded by a shell 16. Opposing end portions 26of the tubes 12 are attached to a plate 14. The end portions 26 of thetubes 12 can be attached to the plate 14 by welding, press-fitting, orby any other means of attachment. A cooling fluid enters the heatexchanger 10 through an inlet 18 located at one end of the heatexchanger 10. The cooling fluid flows through the shell 16 and exchangesheat with a hot fluid that flows through the tubes 12. The fluid in theshell 16 exits the heat exchanger 10 through an outlet 19.

If the heat exchanger 10 is used with an exhaust gas recirculationsystem, an exhaust gas recirculation valve 21 controls the flow of hotfluid from an engine 13 or other component into the heat exchanger 10.If the heat exchanger 10 is used in an exhaust gas recirculation system,the hot fluid is an exhaust fluid. The hot exhaust fluid enters thetubes 12, and heat is transferred from the hot exhaust fluid to acoolant flowing in the shell 16 surrounding the tubes 12. The cooledexhaust fluid in the tubes 12 is then recirculated to the engine 13 orother component. Although an exhaust gas recirculation system has beenillustrated and described, it is to be understood that otherapplications utilizing a tube and shell heat exchanger 10 may also usethe tubes 12 of the present invention.

The tubes 12 include a plurality of indentations 30 that increase thesurface area of the tubes 12, the amount of hot fluid that is proximateto the walls of the tubes 12 to increase the heat transfer, and theamount of turbulence in the fluid in the tubes 12. Creating turbulencein the hot fluid within the tubes 12 mixes the fluid in the center ofthe tube 12 and the fluid proximate to the walls of the tube 12. Thus,the fluid proximate to the walls of the tube 12 will continually changeas the fluid circulates and flows through the tubes 12.

FIGS. 2 and 3 illustrate the method of forming the tube 12 of thepresent invention. A mold 22 of a desired shape is placed in a desiredposition and orientation in a die 20. The tube 12 is positioned in afirst position 23 within the die 20. The mold 22 then crimps the tube 12to form an impression or indentation 30 in the tube 12. The mold 22 isthen released. A moving device 24 both rotates and translates the tube12 relative to the mold 22. Once the tube 12 is in a second position 25,as shown in FIG. 3, the mold 22 again crimps the tube 12 to form anadditional indentation 30 in the tube 12. The process of translating androtating the tube 12 and using the mold 22 to crimp the tube 12 may berepeated as many times as needed to form the desired number andorientation of indentations 30 in the tube 12.

FIG. 4 shows a first embodiment of the tube 12 of the present invention.The mold 22 crimps the tube 12 to form indentations 30 in the tube 12.The mold 22 is released from the mold 22, and the tube 12 is rotated andtranslated relative to the mold 22. The mold 22 then again crimps thetube 12 to form an indentation 30. In one example, the tube 12 isrotated approximately 5 and 10 degrees between successive crimps.

Alternately, shown in FIG. 5, the tube 12 is only translated relative tothe mold 22 and is not rotated when forming the indentations 30. Theindentations 30 are substantially parallel to the flow path of the fluidflowing through the tube 12. Alternately, as shown in FIG. 6, the mold22 can form indentations 30 that are angled relative to the flowpath offluid flowing through the tube 12. In both these examples, the mold 22is released from the tube 12 between successive crimps.

The amount of rotation and translation of the tube 12 relative to themold 22 may be varied to produce a pattern of indentations 30 thatcreates a desired amount of turbulence in the fluid flowing through thetube 12. For example, forming the indentations 30 at an angle relativeto the flow path of the fluid through the tubes 12 can increase theamount of turbulence. One skilled in the art would know the desiredorientation of the indentations 30 in the tube 12 to produce the desiredturbulence.

The tubes 12 include the opposing end portions 26 that preferably have asubstantially uniform circular cross-sectional shape. Thecross-sectional shape of the end portions 26 may differ from the crosssection of the tube 12. That is, the cross-section of the end portions26 corresponds to the cross-section of the desired connector. Thisallows the tube 12 to be easily attached to various other tubes, hoses,or other desired connectors. The end portion 26 may also be formed asdifferent pieces and later attached to each of the tubes 12.

FIGS. 7, 8 and 9 show an alternate embodiment of the tube 12 of thepresent invention. In these embodiments, the mold 22 includes a roller(not shown) installed within the die 20. The mold 22 is crimped on thetube 12, and the tube 12 is translated relative to the mold 22 withoutreleasing the mold 22 from the tube 12. In this example, a continuousgroove 34 is formed on the surface of the tube 12. The groove 34increases the surface area of the tube 12, allowing more fluid tocontact the walls of the tube 12 at a given time.

The mold 22 can include a plurality of rollers to form a plurality ofsubstantially parallel grooves 34 on the tube 12. The rollers contactthe tube 12 and are continuously crimped on the surface of the tube 12to form parallel grooves 34 as the tube 12 translates relative to therollers.

As shown in FIG. 7, one example tube 12 a includes six grooves 34 a.FIG. 8 shows another example tube 12 b having five grooves 34 b. FIG. 9shows another tube 12 c having four parallel grooves 34 c.

FIG. 10 illustrates an alternate tube 12 including a substantiallyspiral shaped groove 38 formed on the wall of the tube 12. A rollercontacts the wall of the tube 12 as the tube 12 is both rotated andtranslated relative to the mold 22 to form a substantially spiral shapedgroove 38 on the tube 12. The roller is continuously crimped against thetube 12 while the tube 12 is both rotated and translated. The angle atwhich the roller is placed against tube 12 and the amount of translationand rotation of the tube 12 can be varied to produce the desired spiralshaped groove 38. Alternately, several rollers can be employed.

Although a preferred embodiment of this invention has been disclosed, aworker of ordinary skill in this art would recognize that certainmodifications would come within the scope of this invention. For thatreason, the following claims should be studied to determine the truescope and content of this invention.

1. A method of forming a tube comprising the steps of: positioning thetube in a first position; forming an indentation on the tube with amold; moving the tube to a second position relative to the mold; andreleasing the mold from the tube.
 2. The method as recited in claim 1further including the step of repeating the step of forming anindentation.
 3. The method as recited in claim 1 wherein the step ofmoving occurs before the step of releasing.
 4. The method as recited inclaim 1 wherein the step of moving occurs after the step of releasing.5. The method as recited in claim 1 wherein the step of moving includesrotating the tube relative to the mold and translating the tube relativeto the mold.
 6. The method as recited in claim 5 wherein the step ofmoving occurs after the step of releasing.
 7. The method as recited inclaim 1 wherein the step of moving includes translating the tuberelative to the mold.
 8. The method as recited in claim 7 wherein thestep of moving occurs after the step of releasing.
 9. The method asrecited in claim 5 further including the step of repeating the step offorming an indentation, wherein the step of rotating includes rotatingthe tube relative to the mold between approximately 5 to 10° betweeneach of the step of repeating.
 10. The method as recited in claim 1wherein the tube includes an end portion, and the end portion has asubstantially circular cross-section.
 11. The method as recited in claim1 wherein the mold includes a roller that engages the tube, and the stepof moving the tube forms a groove on the tube as the roller engages thetube.
 12. The method as recited in claim 11 wherein the step of movingincludes rotating and translating the tube relative to the mold.
 13. Themethod as recited in claim 11 wherein the step of moving includestranslating the tube relative to the mold.
 14. The method as recited inclaim 11 wherein the mold includes a plurality of rollers.
 15. A heatexchanger comprising: a plurality of tubes, each of said plurality oftubes including a body portion and a plurality of indentations; and ashell portion surround said plurality of tubes.
 16. The heat exchangeras recited in claim 15 wherein a first fluid flows through saidplurality of tubes and a second fluid flows through the shell, and thefirst fluid exchanges heat with the second fluid.
 17. The heat exchangeras recited in claim 16 further including a valve controls a flow of thefirst fluid into said plurality of tubes.
 18. The heat exchanger asrecited in claim 15 wherein the plurality of indentations aresubstantially parallel to a flow of a fluid through each of theplurality of tubes.
 19. The heat exchanger as recited in claim 15wherein each of the plurality of tubes has opposing end portions havinga substantially circular cross-section.